The invention relates to an arrangement for and a method of controlling a three-phase generator in a vehicle.
At present, three-phase generators are preferably used for supplying energy in the motor vehicle. These generators generate an alternating voltage or alternating current which is rectified in a rectifier arrangement connected to the generator, and is used for supplying the consumers and for charging the battery. Since the output voltage of the three-phase generator depends considerably on the generator speed, a voltage regulator must be used for achieving the desired constant output voltage.
In independently or separately excited generators, the voltage regulator influences the generator exciting current in such a way that the generator output voltage maintains a constant value, e.g. 14 volts, in spite of considerably changing generator speed between idle and full load and in spite of considerable load fluctuations of the generator.
However, problems result in the power supply in the motor vehicle in winter or in city traffic, since the internal resistance of the battery increases considerably in cold weather, so that its cold start performance is considerably reduced. Moreover, power supply problems and battery charging problems occur at low speeds. Therefore, it is attempted to control the current delivery from the three-phase generators in such a way that the three-phase generators can be utilized to an increased degree. For this purpose, it is suggested, e.g. in Swedish Patent Application 77.02656 corresponding to U.S. Pat. No. 4,237,412 to determine the battery temperature with a temperature sensor and feed this to the voltage regulator. At low battery temperatures, the voltage regulator then increases the output voltage of the generator on the basis of the measurement signal of the temperature sensor and lowers the output voltage of the generator at high temperatures.
A voltage regulator for a generator which charges a battery in a motor vehicle is also disclosed in DE-OS 34 23 767. The temperature of this battery is measured with a temperature sensor, and in so doing, a voltage proportional to the battery temperature is fed to the regulator. In addition, means for determining the internal temperature are provided in the voltage regulator itself and are used for regulating the generator output voltage when the battery temperature sensor has a defect. Taking into account the battery temperature and regulator temperature itself when regulating the voltage enables improvement of the charging balance by increasing the generator output voltage, particularly at low temperatures.
In spite of the known measures, sufficient power supply in the motor vehicle is still a problem, chiefly due to a continuously increasing number of consuming devices as automobile development continues.